A typical door locking system comprises a door, a door frame, hinges securing a first edge of the door to the door frame, and a locking mechanism that, when in the locked position, employs a sliding bolt to secure a second, opposite edge of the door to the door frame. Such a door locking system is generally weakest in the areas where the door and door frame are attached via hinges or sliding bolts.
Many devices have been developed that increase the strength of such door locking systems. Some of these devices are designed to reinforce the primary locking system. For example, locking mechanisms and hinges can be mounted on metallic plates that dissipate excessive force applied to these areas over a larger portion of the door or door frame, thereby strengthening the door locking system.
Other such locking systems use a multiplicity of security bolts. In most of these systems, additional sliding bolts emerge from various edges of the door to engage the door frame, providing more contact points between the door and frame, and thereby strengthening the door locking system.
A substantial drawback to both reinforcing plates and current multiple sliding bolt locking systems is that they are conspicuous. Reinforcing metallic plates are typically mounted on both sides of the door, and multiple sliding bolt mechanisms require a unique linkage and doorknob housing typically located in the center of the door. Further, large bolts and other heavy fasteners are common with such locking systems. Such conspicuous security mechanisms often stir undesirable curiosity and promote break-in attempts that otherwise would not occur.
Moreover, current multiple sliding bolt locking systems are complex, primary mechanisms that require a unique linkage and doorknob housing. Design and manufacturing costs, consequently, are higher than those of a secondary locking system that relies on a primary, commonly available locking mechanism that is easily modified.